Cichy Agnieszka, Kapcia Konrad Jerzy, Ptok Andrzej
Faculty of Physics, Adam Mickiewicz University, ul. Umultowska 85, PL-61-614, Poznań, Poland.
Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudingerweg 9, D-55099, Mainz, Germany.
Sci Rep. 2019 Apr 30;9(1):6719. doi: 10.1038/s41598-019-42044-w.
Ultracold fermionic gases in optical lattices give a great opportunity for creating different types of novel states. One of them is phase separation induced by a trapping potential between different types of superfluid phases. The core-shell structures, occurring in systems with a trapping potential, are a good example of such separations. The types and the sequences of phases which emerge in such structures can depend on spin-imbalance, shape of the trap and on-site interaction strength. In this work, we investigate the properties of such structures within an attractive Fermi gas loaded in the optical lattice, in the presence of the trapping potential and their relations to the phase diagram of the homogeneous system. Moreover, we show how external and internal parameters of the system and parameters of the trap influence their properties. In particular, we show a possible occurrence of the core-shell structure in a system with a harmonic trap, containing the BCS and FFLO states. Additionally, we find a spatial separation of two superfuild states in the system, one in the BCS limit as well as the other one in the tightly bound local pairs (BEC) regime.
光学晶格中的超冷费米子气体为创造不同类型的新状态提供了绝佳机会。其中之一是由不同类型超流相之间的捕获势诱导的相分离。在具有捕获势的系统中出现的核壳结构就是这种分离的一个很好的例子。在这种结构中出现的相的类型和顺序可能取决于自旋不平衡、陷阱形状和在位相互作用强度。在这项工作中，我们研究了加载在光学晶格中的吸引性费米气体中此类结构的性质，存在捕获势时它们与均匀系统相图的关系。此外，我们展示了系统的外部和内部参数以及陷阱参数如何影响它们的性质。特别地，我们展示了在具有谐波陷阱、包含BCS和FFLO态的系统中可能出现核壳结构。此外，我们发现系统中两个超流态的空间分离，一个处于BCS极限，另一个处于紧密束缚的局域对（BEC） regime。
